Method for intravascular two-dimensional ultrasonography and recanalization

ABSTRACT

Ultrasonic apparatus, system and method for high resolution intravascular imaging to assist indovascular lesions and to monitor the results of interventional therapy. An ultrasonic transducer is carried by the distal end of a catheter adapted for insertion into a vessel, and either the transducer or another element is rotated and/or translated relative to the catheter to image different portions of the vessel.

The present application is a continuation-in-part of application Ser.No. 06/834,893 filed on Feb. 28, 1986 now U.S. Pat. No. 4794931, theentire disclosure of which is incorporated herein by reference. Thepresent application is related to application serial no. 07/290,217,filed Dec. 23, 1988, and commonly assigned herewith, the disclosure ofwhich is incorporated herein by reference.

BACKGROUND OF THE INVENTION

This invention relates to a catheter apparatus, system and method forintravascular two-dimensional ultrasonographic imaging and moreparticularly to such an apparatus, system and method for guiding andmonitoring interventional therapy to reduce vascular stenosis.

Ultrasonic two-dimensional imaging apparatus and systems have heretoforebeen provided for use in endoscopy for examining the gastrointestinaltract. Such a device is disclosed in U.S. Pat. No. 4,494,549. Suchdevices, however, have been relatively large and inflexible and arecompletely unsuitable for use within the vascular system of the humanbody. In addition, there is no provision for guiding such devices intospecific branches of blood vessels.

There is therefore a need for a new and improved catheter apparatus,systems and methods which can be utilized for performing intravasculartwo-dimensional ultrasonographic imaging. It would be particularlydesirable if such imaging apparatus and methods could be combined with avariety of intravascular therapeutic modalities, such as angioplasty,atherectomy, laser ablation, and the like, in order to providesimultaneous imaging and recanalization procedures.

SUMMARY OF THE INVENTION

According to the present invention, a method for imaging the interior ofa blood vessel comprises scanning an ultrasonic signal in a preselectedpattern about said interior. By receiving ultrasonic energy reflectedfrom the interior surface of the vessel, including any stenosis orocclusion present, an image or profile of the blood vessel may beproduced Conveniently, the ultrasonic signal is generated by atransducer located at the distal end of a vascular catheter comprising aflexible tubular member. The transducer may be manipulated directly tosweep the ultrasonic signal in a desired pattern, including radialplanar and conical. Alternatively, the transducer may be fixed withinthe catheter and a reflective surface manipulated to sweep theultrasonic signal in a desired pattern. The imaging method of thepresent invention is advantageously combined with interventionaltherapeutic techniques to reduce vascular stenosis, where the stenosismay be imaged prior to, during, and after intervention to help directthe interventional activity to where it will be most effective.

In general, it is an object of the present invention to provide acatheter apparatus, system and method for intravascular two-dimensionalultrasonography.

Another object of the invention is to provide an apparatus, system andmethod of the above character which has a high resolution capability.

Another object of the invention is to provide an apparatus, system andmethod of the above character which can be utilized for assessingendovascular lesions.

Another object of the invention is to provide an apparatus, system andmethod of the above character which can be utilized for monitoring theresults of interventional therapy.

Another object of the invention is to provide an apparatus, system andmethod of the above character which can be used with angioplasty,atherectomy, laser ablation, drug delivery and similar vascularinterventional methods and devices.

Another object is to provide an apparatus, system and method capable ofselective cannulation of branch vessels.

Additional objects and features of the invention will appear from thefollowing description in which the preferred embodiments are set forthin detail in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view partially in cross-section of acatheter apparatus incorporating the present invention.

FIG. 2 is an enlarged cross-sectional view of the distal extremity ofthe apparatus shown in FIG. 1.

FIG. 2A is a detail view illustrating an alternate mounting of a crystaltransducer to provide a conical sweep pattern.

FIG. 2B is an alternate embodiment of the distal extremity of theapparatus shown in FIG. 1, modified to be inserted over a movableguidewire and with the cutting direction reversed.

FIG. 3 is an enlarged cross-sectional view of an intermediate portion ofthe apparatus shown in FIG. 1.

FIG. 4 is an enlarged cross-sectional view taken along the line 4--4 ofFIG. 1.

FIG. 5 is an isometric view of the crystal assembly which forms a partof the apparatus shown in FIG. 1.

FIG. 6 is a schematic block diagram of the electrical and electronicapparatus utilized in the system.

FIG. 7 is a two-dimensional display of an ultrasonogram which can beobtained with the apparatus and system shown in FIGS. 1-6.

FIG. 8 is an enlarged cross-sectional view of another embodiment of acatheter apparatus incorporating the present invention.

FIG. 9 is a cross-sectional view taken along the lines 9--9 of FIG. 8.

FIG. 10 is an enlarged cross-sectional view of still another embodimentof a catheter apparatus incorporating the present invention.

FIG. 10A is a detail view illustrating an alternate configuration of areflective surface to provide a conical sweep pattern.

FIG. 10B is an alternate embodiment of the distal extremity of thecatheter apparatus of FIG. 10, modified to provide a fixed ultrasonictransducer located proximally of a reflective surface on a cutter.

FIG. 11 is an enlarged cross-sectional view of another embodiment of thecatheter apparatus incorporating the present invention.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

In general, the catheter apparatus of the present invention includes aflexible tubular element which is adapted to be inserted into a bloodvessel in the vascular system and a flexible rotatable elongate elementwhich is disposed in the tubular element. In a first embodiment, anultrasonic transducer is carried at the distal end of the flexiblerotatable elongate element, and electrical circuitry carried at thedistal end of the flexible tubular element is connected to theultrasonic transducer for supplying signals to and receiving signalsfrom the transducer. In a second embodiment, a reflective surface iscarried by the distal end of the flexible rotatable elongate element,and the ultrasonic transducer is mounted in the distal tip of theflexible tubular element so that signal generated by the transducer willbe reflected by the reflective surface. In both embodiments, atransmitter is provided for supplying signals to the ultrasonictransducer and a receiver is provided for receiving signals from theultrasonic transducer. A motor drive is usually provided for rotatingthe flexible elongate element, although manual rotation may also beemployed. By rotating the flexible elongate element, the transducersignal can be swept in a desired pattern, either directly by thetransducer in the first embodiment or indirectly by the reflectivesurface in the second embodiment. Timing and control circuitry isprovided for controlling the operation of the transmitter and receiverand optionally the motor drive. A display is provided which is operatedunder the control of the timing and control circuitry for displaying theimage information which is received by the receiver.

The catheters of the present invention may further includeinterventional capability for recanalization of occluded regions withinthe imaged blood vessel. Recanalization is intended to refer to both theopening of total occlusions as well as broadening of the vessel lumen inpartial occlusions. Catheters combining ultrasonic imaging capabilitywith atherectomy devices for severing of the stenotic material aredescribed in detail hereinafter. The methods of the present invention,however, are not limited to atherectomy and include a wide variety ofother interventional techniques which may be performed with vascularcatheters. Suitable interventional techniques include balloonangioplasty, laser ablation angioplasty, balloon embolectomy, aspirationembolectomy, heat probe albation, abrasion, drilling, therapeuticultrasound, and the like. Also, the catheters may be adapted forintroducing clot-dissolving drugs, such as tissue plasminogen activator,streptokinase, urokinase, and the like, in order to reduce the stenosis,as well as platelet-receptor blockers and drugs which limit cellmultiplication in order to inhibit restenosis. Conveniently, perfusionlumens and ports may be provided in the catheter to provide for theadministration of such drugs.

A first exemplary construction of a catheter apparatus 11 constructed inaccordance with the principles of the present invention comprises anelongate tubular assembly 12, as illustrated in FIGS. 1-4. The elongatetubular assembly 12 includes an elongate flexible tubular element 13which is provided with four lumens 14, 16, 17 and 18, with the lumen 14serving as a torque tube, lumen 16 serving as a balloon tube and lumens17 and 18 serving as infusion tubes or lumens as hereinafter described.The tubular element 13 may conveniently be formed as a single extrusionwhich provides the four lumens with the lumens 14 and 16 beingsubstantially circular in cross-section and the lumens 17 and 18 beingarcuate in shape with the configuration of each being determined bythree arcs with one of the arcs being concentric with the outer diameterof the tubular element 13 and with the two smaller arcs being concentricwith lumens 14 and 16 respectively.

A braided shield 21 is provided on the exterior of the tubular element13 and takes the form of one or more layers of braided strands 22 formedof a suitable magnetic material such as an electrical shield. A covertube 23 covers the braided shield 21 and extends the length of thetubular element 13. The cover tube 23 can be formed of a suitablematerial such as a heat shrinkable plastic which is shrunk tightly ontothe braided shield 21 and provides a smooth outer surface so that thetubular assembly 12 can readily enter a vessel of the vascular system ofa patient.

A work performing device such as an atherectomy or cutting device of thetype described in European patent application 163 502 may be provided inthe distal extremity of the tubular assembly 12. A suitable cuttingdevice is described in said European application and consists of ahousing 27 which is provided with a cut-out 28. A rotary cutter 29 isrotatably disposed within the housing 27 and is provided with a hub 31that is secured to a flexible rotatable torque cable 32. The cable 32 isdisposed in and extends through the torque tube lumen 14. The torquecable 32 is formed of a suitable material such as stainless steel. Thehousing 27 is provided with a rounded tip 33 having a recess 34 which isadapted to receive material which is removed by the rotary cutter 29 asthe cutter 29 is advanced as hereinafter described. A spring tip guideor guidewire 36 capable of being shaped is secured to the rounded tip 33and extends forwardly therefrom and serves to guide or steer the housing27 as the tubular assembly 12 with the cutting device 26 secured theretois introduced into the vessel of the vascular system of the patient. Asshown, the spring tip guide 36 can be secured to the rounded tip 33 bysuitable means such as solder 37. It thus can be seen that the guidewire36 is associated with the housing 27. Alternatively, a movable guidewire38 (FIG. 2B) can be utilized to facilitate steering of the catheter 11into the desired vessel of the patient.

A balloon 41 of an expandable type is optionally secured to the housingin a region opposite the cutout 28 and has its distal extremity bondedaround the tip 33 by suitable means, such as an adhesive 42. As shown inFIG. 2, the balloon 41 underlies substantially the entire length of thehousing 27. The balloon 41 is in communication with a balloon tube 43which extends through the balloon tube lumen 16 in the tubular element13. The balloon tube 43 is provided with a lumen 44 through which amedium can be introduced for inflating the balloon 41 and removed fordeflating the balloon 41. The proximal extremity of the balloon 41 andthe proximal extremity of the housing 27 is secured to the distalextremity of the tubular assembly 12 by suitable means, such as heatshrinkable tubing 46.

A system 49 is provided at the distal end 49 of catheter 11 for imagingthe region in which the work performing device is located, said systemusually being a two-dimensional ultrasound image system. The system 49includes an ultrasonic transducer, such as a single crystal 51 (see FIG.5), which is mounted on the hub 31 and is secured thereto by suitablemeans such as an adhesive. The crystal 51 is part of an assembly 52. Thecrystal 51 should be capable of operating at a frequency range of 5 to50 megahertz and typically can be formed of a suitable material such asbarium titanate or cinnabar. As can be seen from FIG. 5, the crystal 51has a rectangular block-like configuration and has two opposed surfacescovered by metallic conducting films 53 and 54 formed of a suitablematerial such as chrome or gold. The material of the films can be formedof a foil or can be in the form of films evaporated or sputtered ontothe opposite surfaces of the crystal 51. The films 53 and 54 serve aselectrodes and are connected to connecting wires 56 and 57 by suitablemeans such as solder. Means is provided for damping out the oscillationsfrom the backside of the crystal 51 and takes the form of a rectangularblock 58 formed of a suitable backing material. The backing material canbe formed in a conventional manner so as to cancel out oscillations fromthe side of a crystal in which the backing material is disposed.

The present invention, however, is not limited to the use ofpiezoelectric crystal oscillators as the ultrasonic transducer, andorganic electrets such as polyvinylidene difluoride (PVDF) andvinylidene fluoride - trifluoroethylene copolymers may also find use.PVDF is particularly suitable as a transducer at higher frequencies,typically at or above 40 MHz.

The wires 56 and 57 are braided onto the torque cable 32 and rotate withthe torque cable. The wires 56 and 57 extend towards the proximalextremity of the tubular assembly 12 and extend into a fitting 61 (seeFIG. 3) formed of a suitable material such as plastic. A pair ofspaced-apart slip rings 62 and 63 formed of a conducting material suchas copper are secured to the torque cable 32. The wire 56 is bonded tothe slip ring 62 and the wire 57 is bonded to the slip ring 63. Afitting 66 is provided which has a threaded bore 67. The tubularassembly 12 extends through the fitting 66 and a reinforcing sleeve 68extends over the portion of the the tubular assembly 12 extendingtherethrough. A pair of spring urged contacts 71 and 72 are carried bythe fitting 66 and are adapted to slidably engage the slip rings 62 and63. The contacts 71 and 72 are connected to conductors 73 and 74. Agrounding lug 76 is provided on the fitting 66 and makes electricalcontact with the braided shield 21. A conductor 77 is connected to thegrounding lug 76.

A male fitting 78 (see FIG. 1) is threaded into the threaded bore 67. Asingle arm adapted 81 is mounted in the male fitting 78 and carries anarm 82 having thereon a balloon inflation port 83 that is incommunication with the lumen 44 in the balloon tube 43 disposed in thetubular assembly 12. The single arm adapter 81 is secured to a rotatingadapter 86 of a conventional type and through which the tubular assembly12 extends. Another single arm adapter 87 is mounted in the rotatingadapter and is provided with a side arm 88 having an infusion port 89disposed therein which is in communication with the infusion lumens 17and 18 provided in the tubular assembly 12. A tapered fitting 91 ismounted in the single arm adapter 87 and is provided with a threadedbore 92 which carries an O-ring 93 that is adapted to be engaged by amale type fitting 94 to form a liquid-tight seal between the tubularassembly 12 and the torque cable 32 which extends therethrough. Thetorque cable 32 is secured to a suitable drive member such as a clutchmember 98 of the type described in European application 163 502 and U.S.Pat. No. 4,771,774, the disclosures of which are incorporated herein byreference. The clutch member 98 is adapted to be secured to a motordrive means of the type described in U.S. Pat. No. 4,771,774 consistingof a motor drive unit which in the present application is identified asa motor 99 (see FIG. 6). The motor 99 is driven by and is under thecontrol of electronic circuitry forming a part of system 49. The part ofthe system 49 shown in block diagram form is substantially conventionaland can be of a suitable type such as certain equipment identified asModel 851B manufactured by Advanced Technology Laboratories, Inc. ofBothel, Washington. As shown in FIG. 6, such apparatus includes a timingand control block 102 which supplies pulses to a transmitter 103. Theoutput of the transmitter 103 is supplied through a transmit receiveswitch 104 which supplies the signals on the conductors 73 and 74through the slip rings 62 and 63 onto the conductors 56 and 57 connectedto the crystal 51. During the time that the transmitter 103 is supplyinghigh frequency energy to the crystal, the crystal 52 is being rotated bythe motor driving the torque cable 32 with the motor 99 being under thecontrol of the timing and control block 102. The motor 99 is of a typesuch as an open loop stepping motor or a closed drop servo controlledmotor which can be driven by the timing and control block 102.

As an alternative to the use of an external motor 99 connected to thecutter 29 by torque cable 32, it would be possible to constructcatheters according to the present invention utilizing micromotorswithin the distal extremity of the catheter. The micromotors could beattached to directly rotate the cutter and transducer (or reflectivesurface as described hereinafter, typically by mounting at the end of anon-rotating cable analogous to torque cable 32.

The transmitter generates a voltage pulse, typically in the 10 to 50volt range, for excitation of the transducer crystal 51. Supplying suchvoltage pulses to the crystal causes the transducer to produce sonicwaves which emanate therefrom into the surrounding tissue structure.Portions of the sonic energy wave reflected by the tissue structure backto the transducer and the transducer 51 acts as a receiver and picks upthe sonic vibrations and converts them into electrical signals which aresupplied by the conducting wires 56 and 57 back to the slip rings 62 and63 through the conductors 73 and 74 and through the transmit receiveswitch 104 to a receiver 106. These signals are amplified and suppliedto a display unit 107 which includes a CRT screen 108 under the controlof the timing and control block 102 to supply an image 109 on thedisplay 108 which can be of the type shown in FIG. 7. As can be seenfrom FIG. 7, as viewed through 360°, the vessel wall 111 of the image109 is shown as indicated, having different cross sections dependingupon the build-up of plaque therein. A central region 112 of the imageis eclipsed because of the imaging catheter. Alternatively, if desired,only a sector of a lesser angle than 360° can be viewed.

The catheter apparatus of the present invention can be constructed invarious sizes. For example, in a 9 French size, the balloon can have alength of approximately 3 centimeters. Sizes down to 3 French and belowcan be accomplished with the construction of the present invention.These particular dimensions are exemplary only and not intended to limitthe scope of the present invention in any way.

Operation and use of the catheter apparatus, system and method duringintravascular ultrasonography can now be briefly described as follows.Let it be assumed that it is desired to utilize the apparatus, systemand method of the present invention to remove the atheroma in a bloodvessel of a patient. The catheter of the catheter apparatus of thepresent invention is introduced into a vessel of the patient as, forexample, into the femoral artery and introducing the catheter into theartery by the use of the guidewire 36. The progress of the catheter intothe vessel of the patient can be observed under x-ray fluoroscopy. Assoon as the cutting device has entered into a region which is desired toremove certain material from the vessel and before a cutting operationis commenced, the atheroma itself can be viewed by operation of theultrasonic imaging system 49. This can be accomplished by operating thetiming control block 102 to cause operation of the motor 99 which inturn causes rotation of the torque cable 32 and the crystal assembly 52to scan the interior of the vessel in which the crystal 51 is disposed,usually at a rotation rate in the range from about 100 to 20,000 rpm,more usually from about 500 to 2,000 rpm. An image of what is beingscanned will appear on the screen 108 of the display device 107.Alternatively, the torque cable 32 may be manually rotated (or aimedwithout rotation) to provide a desired image. Generally, however,motorized rotation will provide a higher definition image. During thetime this rotary scanning is taking place, the cable 32 can be advancedto advance the cutter so that the entire region in which the material isto be removed can be scanned. Usually, the cable 32 is advancedincrementally so that distinct cross-sectional images will besuccessively produced, allowing the operator to determine the length andtopography of the region. Alternatively, the entire catheter apparatus11 may be axially advanced or retracted within the blood vessel lumen toprovide a plurality of cross-sectional images to allow assessment of theentire length of the atheroma.

After the scan, the cable 32 can be retracted slightly (or the catheter11 repositioned) so that the proximal extremity of the cutout 28 lies atthe proximal extremity of the atheroma. In order to stabilize thecutting device, the balloon 41 can be inflated so as to urge the cutout28 of the housing 27 towards the portion of the atheroma it is desiredto remove. The motor 99 can then be energized to rotate the cutter 29.As the cutter 29 is rotated, it can be advanced to progressively removethe material which is disposed within the cutout 28 of the housing 27.As this material is removed it is pushed forwardly and eventually movesinto the recess 34. The balloon 41 can then be deflated and the catheterapparatus removed from the vessel after which the material which hasbeen deposited in the recess 34 can be removed and the cutting devicecleaned for reinsertion into the vessel of the patient for removal ofadditional material from the vessel if required.

During the time that the cutting operation is taking place, the cuttingoperation can be viewed ultrasonically by the rotating crystal 51 whichplaces an image on the screen 108. From this image it can be ascertainedhow well the cutter is performing in removing the material and whetheror not an additional pass of the cutter is required. It should beappreciated that if necessary, several passes of the cutter can be madeand, if necessary, the catheter assembly can be removed from the vesselof the patient to clean out material which has been removed anddeposited in a recess 34.

As illustrated in FIG. 2, the ultrasonic transducer 51' is oriented todirect the ultrasonic signal in a direction substantially radiallyoutward relative to the axis of the flexible tubular element 13. It willsometimes be desirable, however, to incline the ultrasonic transducer51' relative to the tubular axis, as illustrated in FIG. 2A. Byinclining the transducer 51', the ultrasonic signal is directed at aforward angle α relative to the tubular axis. By rotating the inclinedtransducer 51', the ultrasonic signal will sweep a conical patterndirected forward of said transducer. The angle α may be in the rangefrom about 10° to 85°, usually being in the range from 20° to 60°.Scanning with a conical sweep is desirable because it can provideforward viewing at or in front of the location where the cut is beingmade.

An alternate embodiment 11' of catheter 11 is illustrated in FIG. 2B.The catheter 11' is similar to that of catheter 11, except that it ismodified to permit insertion of the catheter 11' over a movableguidewire 38 and the cutter 29' is reversed to provide cutting when thecutter is translated in the proximal (rearward) direction. Themodifications include providing a penetration 39 in the distal tip ofhousing 27 and an axially-aligned penetration 40 in the cutter 29'. Theultrasonic transducer 52' is mounted on the distal end of cutter 29',and torque cable 32' includes an axial lumen. In this way, the catheter11' inserted by conventional techniques over guidewire 38, with theguidewire passing through penetrations 39 and 40 and the lumen of torquecable 32'.

Another embodiment of the catheter apparatus of the present invention isshown in FIGS. 8 and 9. Many of the parts are very similar to the partsutilized in the embodiment of the invention shown in FIG. 1 and havebeen given the corresponding numerals The ultrasonic transducer 52 ismounted in a cavity 53 formed to the rear of the rotary cutter 29. Thedistal extremity of the catheter apparatus shown in FIG. 8 (i.e., to theleft) differs from the apparatus shown in FIG. 1 in that the conductingwires or leads connected to the ultrasonic crystal 52 are connected tothe outside world at a point which is proximal of an adapter 122 whereasin the embodiment shown in FIG. 1, the connectors are connected at apoint which is distal of the adapters 82 and 88. Thus there is shown anadapter 122 which is provided with an arm 123 through which dyeinjection and pressure measurements can be made and another fitting 124which can be utilized in inflating and deflating the balloon 41. Anotheradapter 126 is provided which is threaded into the proximal end of theadapter 122 and forms a sealing engagement with an O-ring 127 carried bythe adapter 122. The torque cable 32 extends through the adapter 126 andis connected to a clutch member 128. The clutch member 128 which carriesa finger operated member 129 is adapted to be secured to motorized drivemeans of the type hereinbefore described for causing rotation of thetorque cable 32.

As hereinbefore explained, the conducting wires connected to theultrasonic transducer 52 are braided into the guidewire 32. Means iscarried by the adapter 126 which as adapted to make contact with theconducting wires connected to the crystal 52 and consists of brushes 131and 132 which are yieldably urged by springs 133 towards the torquecable 32 so as to make contact with the conducting wires or leadscarried by the guidewire 32. The springs 133 are held in place by pins134 which are frictionally seated within the adapter 126. Conductingwires 136 and 137 are connected to the pins 134. These wires 136 and 137are connected into the system in a manner hereinbefore described withthe previous embodiments. The operation of this embodiment is verysimilar to that described in conjunction with the operation of theembodiment shown in FIG. 1

Operation of this embodiment of the invention is very similar to thathereinbefore described with the principal advantage being that leadswhich are connected to the crystal and for receiving signals from thecrystal are disposed proximally of the two arm adapter 122.

As a modification of catheter 121, cutter 29 could be provided with anabrasive external surface, either in place of or in addition to theforward cutting edge. Such an abrasive surface would be useful to removeatheroma and plaque by contact abrasion.

Still another embodiment 151 of the catheter apparatus of the presentinvention is shown in FIG. 10. Certain parts of this catheter apparatus151 are very similar to those hereinbefore described and are identifiedby the same numbers. Thus there has been provided a housing 27 which hasan outwardly facing cutout 28. A coil spring guide wire 36 is secured tothe distal extremity of the housing 27 as shown (although the catheter151 could easily be adapted to receive a movable guidewire as describedabove in connection with the embodiment of FIGS. 1-4). The balloon 41 iscarried by the housing and has its distal extremity secured to thehousing by a band 92. The balloon 41 is disposed outside of the housing27 on the side opposite the cutout 28. A flexible tubular assembly 154is secured to the proximal end of the housing 27. A three-arm adapter152 is mounted on the proximal extremity of the tubular assembly 154.The tubular assembly 154 comprises a flexible tubular element formed ofa suitable material such as plastic which is provided with a ballooninflation lumen 155 that is in communication with the interior of theballoon 41 and extends into a balloon inflation port 156 provided as apart of the three-arm adapter 152.

A crystal 157 is carried by the housing 27 in a stationary position. Asshown, the crystal 157 is mounted vertically or in a direction which isat right angles to the longitudinal axis of the housing 27. It can bemounted in the distal extremity of the housing 27 in a suitable mannersuch as by an adhesive. A suitable sound absorbing material 158 isprovided behind the ultrasonic crystal 157 and fills the space betweenthe crystal 157 and the distal extremity of the housing 27. A pair ofconducting wires 161 are connected to the ultrasonic crystal 157 andextend rearwardly through the housing 27 and are connected into sockets162 provided in a side arm 163 forming a part of the adapter 152.

The flexible tubular element 154 is provided with a large lumen 164extending the length thereof and which has a rotatable flexible drivecable 166 disposed therein. The flexible torque cable 166 is formed inthe manner hereinbefore described and is secured to a generallycylindrical member 167 which as hereinafter described, serves as areflector mount and also serves to carry a rear-facing rotary cutter169. Thus as shown, the member 167 is provided with a reflective surface168 which is included at an angle of approximately 45° and faces thetransducer 157 in such a manner so that sound waves propagated by thetransducer impinge upon the surface 168 and are propagated outwardly ina direction substantially transverse, i.e., at right angles, to thelongitudinal axis of the housing 27. A circular cutting edge 169 isprovided on the member 167 at the proximal extremity thereof. Atruncated conical recess 171 is provided in the proximal extremity ofthe member 167. The conical recess 171 can be used as a reservoir forcollecting material as it is severed by the circular cutting edge 169.

The angle of inclination of the reflective surface 168 relative to theaxis of housing 27 may be varied, particularly being increased, asillustrated in FIG. 10A, where angle β may be in the range from 10° tousually being in the range from 10° to 40°. By inclining the reflectivesurface by an angle β less than 45°, the reflected ultrasonic signalwill sweep in a rearward conical pattern which allows viewing at or infront of (i.e., to the right in FIG. 10) the cutting edge 169 of member167.

The three-arm adapter 152 is provided with another arm 173 which servesas an infusion port and which is in communication with the lumen 164through which the drive cable 166 extends. This lumen 164 opens into theinterior of the housing 27 and is in communication with the cutout 28.Another adapter 176 is threaded into the proximal extremity of theadapter 162 and engages an O-ring 177. The drive cable 166 extendsthrough the adapter 176 and has its distal extremity secured to theclutch member 128. As hereinbefore explained, the clutch member 128 canbe secured to a motorized drive means (or may be manually rotated) forcausing rotational movement of the cutter and mirror member 167.

An alternate embodiment 151' of catheter 151 is illustrated in FIG. 10B.The catheter employs a fixed ultrasonic transducer 157', but cutter 169'is reversed to provide for forward cutting. Forward cutting is oftenadvantageous in that severed stenotic material is less likely to becomeentangled with the torque cable 166'. Ultrasonic transducer 157' will beprovided with a central penetration to allow passage of the torque cable166', and said transducer will be located at the proximal end of housing27', but otherwise the construction of catheter 151' will be the same ascatheter 151.

In a further modification, it is possible to secure the ultrasonictransducer 157' onto the torque cable 166'. Wires connecting thetransducer 157' to the external receiver and transmitter would then beattached to the torque cable 166' and coupled to the outside in a mannersimilar to that illustrated in FIGS. 1-4. The transducer 157' would thentranslate axially in tandem with the cutter 169' and the mirror 168'. Bymaintaining a fixed distance between the cutter 169' and transducer157', signal processing to produce an image is simplified.

Operation of the catheter apparatus 151 shown in FIG. 10 may now bedescribed as follows. The operation of this device in many respects isvery similar to that hereinbefore described with respect to theplacement of the catheter in the vessel. The housing 27 can bepositioned in the stenosis hereinbefore described and ultrasonic imagingcan be carried out by supplying pulses of electrical energy to theultrasonic transducer 157 which emanates ultrasonic energy and directsthe same onto the reflector 168 which reflects the ultrasonic energy upinto the tissue surrounding the housing. Rotation of the mirror 168causes an image to be formed which can be viewed in the mannerhereinbefore described. This imaging can be carried out by rotating thecable 166 and at the same time advancing the drive cable 166 throughoutthe length of the cutout 28 to view the stenosis. After the viewingoperation has been accomplished and it is ascertained that it isdesirable to remove the material creating the stenosis by use of thework performing device in the form of the cutter member 167, the cuttermember 167 can be advanced to the distal extremity of the cutout 28.With the cutout 28 in the proper location, the balloon 41 can then beinflated through the balloon inflation port 156 to urge the housing 27in a direction so that the stenosis enters the cutout. As soon as thishas been accomplished, the cutter member 157 can be rotated at a highrate of speed and gradually retracted (i.e., translated to the right inFIG. 10) to cause the material forming the stenosis to be severed by theblade 169 cutter member 167 and collected within the recess 171. Thiscutting and collecting operation can be continued until the cuttermember 167 has been advanced to the extreme proximal position At thistime, the catheter apparatus 151 can be removed and the tissue collectedwithin the recesses 171 can be removed. Thereafter, additionalinsertions of the catheter apparatus can be made and the same cuttingoperations performed until the desired amount of material has beenremoved from the area of the stenosis to provide for increased bloodflow through the vessel.

Another embodiment of a catheter apparatus 180 incorporating the presentinvention is shown in FIG. 11. The catheter apparatus 180 is utilizedsolely for imaging purposes and employs a fixed ultrasonic transducer182 which transmits its signal against a rotating reflective surface204. The catheter apparatus 180 is constructed very similar to thecatheter apparatus 151 shown in FIG. 10 with the exception that thecutting mechanism has been eliminated. The use of such a catheterapparatus 180 is desirable where it is unnecessary to provide a cuttingfunction (or other interventional treatment modality). The catheterapparatus 180 also has many parts which are similar to the catheterapparatuses heretofore described. Thus there is provided a housing 27which carries on its distal extremity a coil spring guide 36. As before,however, the catheter 180 can also be adapted to be inserted over amovable guidewire within the scope of the present invention. Theultrasonic transducer 182 is provided in the distal extremity of thehousing 27 and is disposed vertically or in a direction which isperpendicular to the longitudinal axis of the housing. A sound absorbingbacking material 183 is provided in the distal extremity of the housingbehind the transducer 182. Conducting wires or leads 184 are connectedto the transducer 182. The proximal extremity of the housing 27 isconnected to the distal extremity of flexible elongate tubular element186 which is connected to a two-arm adapter 187. The leads 184 extendthrough the tubular element 186 and are connected to sockets 188provided in the arm 189 of the two-arm adapter 187. The tubular element186 is provided with a large lumen 191 which carries the drive cable192. The drive cable 192 is connected to a clutch member 193 of the typehereinbefore described which is adapted to be driven by motive means inthe manner hereinbefore described. The clutch member 193 is providedwith a flange 194 which cooperates with a flange 196 on the adapter 187.The adapter 187 carries an O-ring 197 seated against another flange 198forming a part of the adapter 187. The O-ring 197 forms a liquid-tightseal with respect to the drive cable 192. The clutch member 193 is thusheld in a fixed longitudinal position while still permitting rotation ofthe same. The adapter 187 is provided with a tapered surface 199 adaptedto fit into a motor drive means. Alternatively, the clutch member 193can be adapted for manual rotation

The drive cable 192 has its distal extremity secured to a rotatingmember 203 which is provided with an inclined reflected surface 204which serves as a reflector for reflecting ultrasonic energy generatedby the transducer 182 in a transverse direction relative to thelongitudinal axis of the housing 27. The angle of inclination of surface204 may vary, typically between 45° and 85° to provide for forwardviewing as described above, depending on the sweep geometry desired. Asillustrated, the torque cable 192 is unable to axially translate withinthe lumen 191. Thus, the reflective surface 204 on rotating member 203remains in a fixed longitudinal position relative to the housing 27 andcannot be advanced or retracted with respect to the ultrasonictransducer 182. The reflective surface 204 can, of course, be axiallytranslated within a blood vessel by movement of the catheter 180 as awhole. Also, the catheter 180 could be modified to permit axialtranslation of the rotating member 203 within the housing 27 (in amanner similar to the previous catheter embodiments), but generally thiswill be unnecessary.

The large lumen 191 in flexible elongate tubular element 186 is incommunication with a side arm port 206 which forms a part of the two-armadapter 187. The housing 27 should be formed of a material which causesminimal attenuation of the ultrasonic signal which is transmitted andreceived by transducer 182. Suitable materials include polyethylene,silicone rubber, polyvinyl chloride, polyurethanes, polyesters, naturalrubbers, and the like. Alternatively, the housing may be formed ofacoustically opaque materials if a cutout 207 (shown by the dashedlines) is provided through which the ultrasonic energy can pass.

The operation of the catheter apparatus 180 shown in FIG. 11 is verysimilar to that hereinbefore described with the exception that thecutting operation is omitted. With this catheter apparatus, the devicecan be inserted in the same manner as with respect to the other deviceshereinbefore described. When the device is in the desired location, asfor example, in the stenosis, the stenosis can be imaged ultrasonicallyby causing the rotating member 203 to be rotated with respect to thecrystal 182 to cause ultrasonic energy to be directed upwardly andoutwardly through the housing 181 to impinge upon the sidewalls of thevessel in which the catheter apparatus 180 is positioned. If a differentlongitudinal position is desired to be scanned, the entire catheterapparatus 181 can be shifted longitudinally in the vessel to the desiredlocation. After the ultrasonic imaging has been completed, the catheterapparatus 180 can be removed and other operations performed if desiredwith other instruments.

It should be appreciated that if desired, another embodiment of catheterapparatus used solely for imaging can be provided by mounting thecrystal at the end of the torque cable as illustrated in FIG. 8 so thatthe crystal is rotated about an axis parallel to the longitudinal axisof the housing.

From the foregoing, it can be seen that a two-dimensional ultrasoundimage is generated by rotating a crystal or a mirror which is located atthe tip of the catheter. Good resolution is obtained because of therelatively high frequency, i.e., 5 to 50 megahertz that is used. Theimage which is created is generally perpendicular to the longitudinalaxis of the catheter, but may also be in a forward conical pattern,depending on the precise geometry of the transducer and/or mirror. Themotor or manual drive means which is utilized for rotating thetransducer is external to the patient. Rotation of the transducer ismade possible because of the electrical connection made with the brushcontacts. The use of the balloon stabilizes the housing so that thecutting operation can be readily accomplished.

The apparatus and system of the present invention makes it possible toobtain images in very small vessels and has made it possible toaccomplish the same by utilizing the precision driving of a veryflexible cable. The catheter apparatus in addition to being capable ofimaging is also capable of being steered by the flexible guidewiresecured to the tip.

It is apparent from the foregoing that there has been provided acatheter apparatus, system and method which is particularly useful forintravascular two-dimension ultrasonography which can be utilized withmany different types of operations, as for example, in performingatherectomies.

What is claimed is:
 1. A method for imaging the interior wall of a bloodvessel, said method comprising:generating an ultrasonic signal using atransducer located within the blood vessel; sweeping the signalcontinuously in a predetermined pattern about the interior wall of theblood vessel, wherein said sweeping is accomplished by rotating thetransducer or a reflective surface which deflects the signal from thetransducer within a catheter which remains substantially stationarywhile the signal is being swept; receiving ultrasonic signal reflectedfrom the interior wall of the blood vessel; and producing an image fromthe reflected signal.
 2. A method as in claim 1, wherein the ultrasonicsignal has a frequency in the range from about 5 to 50 megahertz.
 3. Amethod as in claim 1, wherein the generated ultrasonic signal isdirected generally axially relative to the blood vessel and deflectedtransversely by the rotating reflective surface.
 4. A method as in claim1, wherein the generated signal is directed generally transversely by arotating transducer.
 5. A method as in claim 1, wherein the ultrasonicsignal is directed at a forward angle of from about 10° to 85° relativeto the axis of the blood vessel, whereby a conical scan is performed. 6.A method as in claim 1, further comprising axially advancing theultrasonic signal within the blood vessel to provide a series ofsuccessive cross-sectional images of the blood vessel.
 7. A method forimaging the interior of a blood vessel, said methodcomprising:positioning a distal end of a flexible tubular member withinthe blood vessel proximate a preselected region; sweeping a transducerelement through a preselected pattern within said distal end while theflexible tubular member remains substantially stationary; generating anultrasonic signal from the transducer, which signal impinges against theinterior wall of the blood vessel; receiving ultrasonic energy reflectedfrom the blood vessel wall with the transducer; and producing an imageof the blood vessel based on the reflected ultrasonic energy.
 8. Amethod as in claim 7, wherein the transducer is oriented to direct theultrasonic signal substantially transversely to the axis of the tubularmember, whereby a transverse planar scan is performed.
 9. A method as inclaim 7, wherein the transducer is oriented to direct the ultrasonicsignal at a forward angle in the range from about 10° to 85° relative tothe axis of the tubular member, whereby a conical scan is performed. 10.A method as in claim 7, further comprising axially advancing the distalend of the flexible tubular member within the blood vessel to producesuccessive cross-sectional images.
 11. A method for imaging the interiorof a blood vessel, said method comprising:positioning a distal end of aflexible tubular member within the blood vessel proximate a preselectedregion; directing an ultrasonic signal against a reflective surfacewithin the distal end of the flexible tubular member; manipulating thereflective surface to reflect the ultrasonic signal in a preselectedpattern within the blood vessel while the flexible tubular memberremains substantially stationary; receiving ultrasonic energy reflectedfrom within the blood vessel; and producing an image of the interior ofthe blood vessel based on the reflected ultrasonic energy.
 12. A methodas in claim 11, wherein the reflective surface is inclined at a fixedangle relative to the tubular axis and wherein manipulating thereflective surface comprises rotating said surface about said axis. 13.A method as in claim 12, wherein the ultrasonic signal is directedsubstantially axially and said mirror is inclined at about 45°, wherebya transverse cross-sectional image is produced.
 14. A method as in claim12, wherein the ultrasonic signal is directed substantially axially andsaid mirror is inclined at an angle between about 5° and 45°, wherebythe ultrasonic signal is swept about a conical pattern.
 15. A method forrecanalization of a blood vessel, said method comprising:positioning adistal end of a flexible tubular member within the blood vesselproximate a region of stenosis; generating an ultrasonic signal with anultrasonic transducer disposed in the distal end of the flexible tubularmember while the flexible tubular member remains substantiallystationary; sweeping the ultrasonic signal through a preselected patternabout the interior wall of the blood vessel, including the region ofstenosis, wherein said sweeping is accomplished by rotating theultrasonic transducer or a reflective surface disposed within thetubular member to deflect said signal in a predetermined pattern;receiving ultrasonic signal reflected back from the interior wall;producing an image of the region of stenosis; and reanalyzing the regionof stenosis using interventional means located on the distal end of theflexible tubular member, wherein the location of intervention is basedat least partly on the image.
 16. A method as in claim 15, wherein theultrasonic signal is swept about the preselected pattern by physicallyrotating the transducer.
 17. A method as in claim 15, wherein theultrasonic signal is swept about the preselected pattern by directingthe signal against a reflective surface and manipulating the reflectivesurface.
 18. A method as in claim 17, wherein the reflective surface isrotated.
 19. A method as in claim 15, wherein the interventional meansis a rotating blade used to severe stenotic material.
 20. A method as inclaim 15, wherein the interventional means is an abrasive surface.
 21. Amethod as in claim 15, wherein the interventional means is a drill. 22.A method as in claim 15, wherein the interventional means is a perfusionport for delivery drugs.